1. Field of the Invention
The present invention relates to a radio telecommunication apparatus for use in a radio telecommunication system such as a cellular mobile telephone system which performs channel connection by a PIN (Personal Identification Number) service.
2. Description of the Related Art
In the conventional cellular mobile telephone system, PIN services are offered to prevent a mobile radio telephone (such as a vehicle telephone, a portable telephone, etc.) from being used by an unexpected person. The PIN is a personal identification number specifying one of mobile radio telecommunication terminals and is different from a MIN (Mobile Identification Number). This MIN is recorded on the telephone directory or the like, whereas the PIN is not recorded on the telephone directory or the like and is assigned for each terminal by a proprietor. The PIN service using this PIN will be explained below.
In the PIN service, when a mobile radio telephone has originated a call, a call signal corresponding to this call origination is transmitted to a base-station/control-station through a radio channel. Upon receiving the call signal, the base-station/control-station suspends a communication channel and requests the mobile radio telephone to transmit a PIN assigned thereto. Upon receiving the PIN, the base-station/control-station compares it with a prestored PIN, and performs a switching operation concerning a telephone number transmitted from the mobile radio telephone, only if the both PINs are identical to each other. In the case where no PIN services are offered, a series of switching operations beginning with processing of a call origination and input of a telephone number are performed, and the communication channel is released when the communication has terminated.
FIG. 1 shows a sequence of PIN services in the conventional cellular mobile telephone system. As is shown in FIG. 1, first, the user of a mobile radio telephone performs a call origination (step S201). More specifically, the user pushes a call key of a key section incorporated in the telephone, and at the same time designates the telephone number of a destination. As a result, a call signal including the destination number is transmitted to the base-station/control-station (step S202).
When the base-station/control-station has received the call signal, it extracts the telephone number designated by the call signal, and then transmits a communication channel designating signal to the mobile radio telephone (step S203), thereby suspending the communication channel (step S204).
Thereafter, the base-station/control-station transmits a PIN guidance signal to the mobile radio telephone (step S205). Thus, the user is informed of a guidance through the speaker, etc. of the telephone.
The user performs a flash operation using the guidance (step S206). Specifically, the user pushes a particular function key in the key section to notify the base-station/control-station of that a PIN code will be transmitted. As a result, a flash operation signal of a single tone (e.g. 400 ms, 10 Kz) is transmitted from the mobile radio telephone (step S207).
Upon receiving the flash operation signal, the base-station/control-station prepares for reception of the PIN code signal, and supplies the mobile radio telephone with a PIN-input request signal (step S208).
When the mobile radio telephone has received the PIN-input request signal from the base-station/control-station, the user performs an operation for inputting the PIN code which he has in mind (step S209).
Subsequently, a PIN code signal based on the input PIN code is transmitted to the base-station/control-station (step S210).
Upon receiving the PIN code signal from the mobile radio telephone, the base-station/control-station retrieves a pre-registered PIN corresponding to the telephone number extracted on the basis of the call signal, and determines whether or not the PIN indicated by the PIN code signal is identical to the pre-registered one (step S211). If they are identical to each other, the base-station/control-station connects the mobile radio telephone, which has originated the call, to the destination with the designated telephone number (step S212). Thereafter, the user who has originated the call communications with a person at the destination. After the communication, the communication channel (radio channel W) is released.
As explained above, in the conventional PIN services employed in a cellular mobile radio telephone, etc., the user inputs the PIN code of the telephone, and the channel to a destination is connected if the PIN code is identical to that registered in the base-station/control-station. Accordingly, a communication with an unexpected person can be avoided.
However, in the above-described conventional cellular telephone system, the PIN code must be input each time a call is originated by a mobile radio telephone, which makes the call operation complicated. If an erroneous PIN is input, the input of the PIN must be repeated, which makes the call origination more complicated. In addition, if the user forgets the PIN of the mobile radio telephone, he cannot use the PIN services and accordingly the telephone.